1. Field of the Invention
The present invention relates to semiconductor packages, and, more particularly, to a semiconductor package having a MEMS (micro-electro-mechanical system) element.
2. Description of Related Art
MEMS elements have integrated electrical and mechanical functions and can be fabricated through various micro-fabrication technologies. A MEMS element can be disposed on a chip and covered by a shield or packaged with an underfill adhesive so as to form a MEMS package structure. FIGS. 1A to 1D show various types of MEMS package structures in the art.
FIG. 1A shows a MEMS package structure as disclosed by U.S. Pat. No. 6,809,412. Referring to FIG. 1A, a chip 14 having a MEMS element 141 is disposed on a substrate 10 and electrically connected to the substrate 10 through a plurality of bonding wires 11. Then, a glass lid 12 is disposed on the substrate 10 to cover the chip 14, the MEMS element 141 and the bonding wires 11.
FIG. 1B shows a MEMS package structure as disclosed by U.S. Pat. No. 6,303,986. Referring to FIG. 1B, a glass lid 12 is disposed on a chip 14 so as to cover a MEMS element 141 of the chip 14. Then, the chip 14 is disposed on a lead frame 10′ and electrically connected to the lead frame 10′ through bonding wires 11 Finally, an encapsulant 15 is formed to encapsulate the lead frame 10′, the bonding wires 11, the glass lid 12 and the chip 14.
However, the carriers of the above-described structures (the substrate 10 of FIG. 1A and the lead frame 10′ of FIG. 1B) increase the thickness of the structures, thus adversely affecting miniaturization of the package structures. Therefore, carrier-free package structures were developed.
FIG. 1C shows a MEMS package structure as disclosed by U.S. Pat. No. 7,368,808. Referring to FIG. 1C, a chip 14 having a plurality of conductive pads 140 and a MEMS element 141 is provided. A glass lid 12 having a plurality of through holes 120 is disposed on the chip 14 for covering the MEMS element 141. Each of the through holes 120 has conductive pads 122 disposed on the two ends thereof. The conductive pads 122 on the lower ends of the through holes 120 electrically connect with the conductive pads 140 of the chip 14, respectively, and the conductive pads 122 on the upper ends of the through holes 120 have solder balls 16 formed thereon so as for the chip 14 to be electrically connected to other electronic components.
FIG. 1D shows a MEMS package structure as disclosed by U.S. Pat. No. 6,846,725. Referring to FIG. 1D, a chip 14 having a plurality of conductive pads 140 and a MEMS element 141 is provided, and the conductive pads 140 have solder bumps 142 disposed thereon. A glass lid 12 having a plurality of through holes 120 is disposed on the chip 14 for covering the MEMS element 141. Each of the through holes 120 has conductive pads 122 disposed on the two ends thereof. The conductive pads 122 on the lower ends of the through holes 120 electrically connect with the solder bumps 142, respectively, and the conductive pads 122 on the upper ends of the through holes 120 are used for electrically connecting the chip 14 to other electronic components.
Although the last two above-described package structures eliminate the need of a carrier so as to achieve miniaturization, the cost for drilling through holes 120 in the lids 12 is quite high. Further, it is difficult to align the conductive pads 122 at the two ends of each of the conductive through holes 120 with a high degree of accuracy or stably secure the conductive pads 122 to the conductive through holes 120, thus easily leading to poor electrical connection and accordingly reducing the reliability of electrical connection between the chip 14 and an external electronic component.
Therefore, it is imperative to provide a package having a MEMS element so as to overcome the above-described drawbacks.